1. Field of the Invention
The present invention relates generally to the field of computer graphics. More specifically, the present invention relates to the field of computer graphics for interlaced displays.
2. Related Art
The two most commonly used means of refreshing (i.e., displaying images on) a Cathode Ray Tube (CRT) display are progressive scanning and interlaced scanning. Progressive scanning, used by most computer displays, starts at the top of the image, scans the first line of the image and then scans each subsequent line of the image. Interlaced scanning starts at the top of the image, scans the first even-numbered line of the image, scans each subsequent even-numbered line of the image, returns to the top of the image and then proceeds to scan the odd-numbered lines of the image. Interlaced scanning reduces bandwidth by requiring less data during each of the two passes on the CRT. Interlaced scanning, however, does not come without drawbacks.
Because interlaced scanning displays only one half of the lines of an image at a time, images with high-frequency vertical information tend to flicker or have other visual aberrations, reducing visual accuracy. In addition, conventional interlaced scanning fills the frame buffer with an entire image before scanning. Thus, at any given time, the frame buffer contains twice as many lines than are needed for each of the two passes (once for even-numbered lines and once for odd-numbered lines), which is an inefficient use of fill resources.
Accordingly, there exists a need for a method for reducing fill and improving quality of interlaced displays.